This application proposes three types of experiments. All are intended to develop improved behavioral methods for categorizing abused drugs, or to determine the abuse liability of newly developed drugs. All are based on the drug discrimination technique. Project 1 is applied in nature. It seeks to develop high specificity assay techniques which can determine whether newly developed antianxiety drugs produce subjective effects more like those of highly abused depressants such as ethanol, or more like those of less abused drugs such as diazepam. If successful, the method will provide a new preclinical method for predicting the abuse liability of new drugs. Projects 2 and 3 seek to improve the efficiency of the drug discrimination technique, and to extend the range of situations in which it will be applicable. Project 2 will identify drug discrimination substitution test procedures yielding data that is quantitative instead of only qualitative in nature, and that is more linearly representational of the underlying drug effects than that yielded by present test procedures. Project 3 will evaluate new methods for controlling the specificity of the drug discrimination procedure, which will allow it to be applied to a wider variety of psychopharmacological investigations than at present. A total of seven individual experiments are proposed in connection with these projects.